Marie Curie

New elements

In 1895, Wilhelm Röntgen discovered the existence of X-rays, though the mechanism behind their production was not yet understood. In 1896, Henri Becquerel discovered that uranium salts emitted rays that resembled X-rays in their penetrating power. He demonstrated that this radiation, unlike phosphorescence, did not depend on an external source of energy but seemed to arise spontaneously from uranium itself. Influenced by these two important discoveries, Curie decided to look into uranium rays as a possible field of research for a thesis.

She used an innovative technique to investigate samples. Fifteen years earlier, her husband and his brother had developed a version of the electrometer, a sensitive device for measuring electric charge. Using her husband's electrometer, she discovered that uranium rays caused the air around a sample to conduct electricity. Using this technique, her first result was the finding that the activity of the uranium compounds depended only on the quantity of uranium present. She hypothesized that the radiation was not the outcome of some interaction of molecules but must come from the atom itself. This hypothesis was an important step in disproving the assumption that atoms were indivisible.

In 1897, her daughter Irène was born. To support her family, Curie began teaching at the École normale supérieure. The Curies did not have a dedicated laboratory; most of their research was carried out in a converted shed next to ESPCI. The shed, formerly a medical school dissecting room, was poorly ventilated and not even waterproof. They were unaware of the deleterious effects of radiation exposure attendant on their continued unprotected work with radioactive substances. ESPCI did not sponsor her research, but she received subsidies from metallurgical and mining companies and from various organisations and governments.

Curie's systematic studies included two uranium minerals, pitchblende and torbernite (also known as chalcolite). Her electrometer showed that pitchblende was four times as active as uranium itself, and chalcolite twice as active. She concluded that, if her earlier results relating the quantity of uranium to its activity were correct, then these two minerals must contain small quantities of another substance that was far more active than uranium. She began a systematic search for additional substances that emit radiation, and by 1898 she discovered that the element thorium was also radioactive. Pierre Curie was increasingly intrigued by her work. By mid-1898 he was so invested in it that he decided to drop his work on crystals and to join her.

The [research] idea [writes Reid] was her own; no one helped her formulate it, and although she took it to her husband for his opinion she clearly established her ownership of it. She later recorded the fact twice in her biography of her husband to ensure there was no chance whatever of any ambiguity. It [is] likely that already at this early stage of her career [she] realized that... many scientists would find it difficult to believe that a woman could be capable of the original work in which she was involved.

She was acutely aware of the importance of promptly publishing her discoveries and thus establishing her priority. Curie chose to present her work to the Académie des Sciences, the same rapid means of publication that Becquerel had used two years earlier. Since she was not a member of the Académie, her paper, giving a brief and simple account of her work, was presented for her to the Académie on 12 April 1898 by her former professor, Gabriel Lippmann. However, while Becquerel had presented his discovery the day after he made it and got credit for the discovery of radioactivity before Silvanus Thompson, Curie was beaten by Gerhard Carl Schmidt in the race to report that thorium gives off rays in the same way as uranium.

At that time, no one else in the world of physics had noticed what Curie recorded in a sentence of her paper, describing how much greater were the activities of pitchblende and chalcolite than that of uranium itself: "The fact is very remarkable, and leads to the belief that these minerals may contain an element which is much more active than uranium." She later would recall how she felt "a passionate desire to verify this hypothesis as rapidly as possible". On 14 April 1898, the Curies optimistically weighed out a 100-gram sample of pitchblende and ground it with a pestle and mortar. They did not realise at the time that what they were searching for was present in such minute quantities that they would eventually have to process tonnes of the ore.

In July 1898, Curie and her husband published a joint paper announcing the existence of an element they named 'polonium', in honour of her native Poland, which would for another twenty years remain partitioned among three empires (Russia, Austria, and Prussia). On 26 December 1898, the Curies announced the existence of a second element, which they named 'radium', from the Latin word for 'ray'. In the course of their research, they also coined the word 'radioactivity'.

To prove their discoveries beyond any doubt, the Curies sought to isolate polonium and radium in pure form. Pitchblende is a complex mineral; the chemical separation of its constituents was an arduous task. The discovery of polonium had been relatively easy; chemically it resembles the element bismuth, and polonium was the only bismuth-like substance in the ore. Radium, however, was more elusive; it is closely related chemically to barium, and pitchblende contains both elements. By 1898 the Curies had obtained traces of radium, but appreciable quantities, uncontaminated with barium, were still beyond reach. The Curies undertook the arduous task of separating out radium salt by differential crystallisation. From a tonne of pitchblende, one-tenth of a gram of radium chloride was separated in 1902. In 1910, she isolated pure radium metal. She never succeeded in isolating polonium, which has a half-life of only 138 days.

Between 1898 and 1902, the Curies published, jointly or separately, a total of 32 scientific papers, including one that announced that, when exposed to radium, diseased, tumour-forming cells were destroyed faster than healthy cells.

In 1900, Curie became the first woman faculty member at the École normale supérieure de jeunes filles and her husband joined the faculty of the University of Paris. In 1902 she visited Poland on the occasion of her father's death.

In June 1903, supervised by Gabriel Lippmann, Curie was awarded her doctorate from the University of Paris. Earlier that month the couple were invited to the Royal Institution in London to give a Friday Evening Discourse on Radium. At the time, Marie was four months pregnant, and suffering from extreme fatigue. Discourses were given by an individual, and though no rule existed barring women from speaking, convention and circumstance meant that Pierre Curie gave the address.

Pierre's lecture, entirely in French, clearly indicated Marie's contributions to their research. The Royal Institution did however, break with tradition; Lady Dewar honoured Marie by presenting her with a bouquet of La France Rosa, and Marie carried them into the theatre, where she sat on the front row alongside the most esteemed members of the Royal Institution. Meanwhile, a new industry began developing, based on radium. The Curies did not patent their discovery and benefited little from this increasingly profitable business.

Nobel Prizes

In December 1903 the Royal Swedish Academy of Sciences awarded Pierre Curie, Marie Curie, and Henri Becquerel the Nobel Prize in Physics, "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel." At first the committee had intended to honour only Pierre Curie and Henri Becquerel, but a committee member and advocate for women scientists, Swedish mathematician Magnus Gösta Mittag-Leffler, alerted Pierre to the situation, and after his complaint, Marie's name was added to the nomination. Marie Curie was the first woman to be awarded a Nobel Prize.

Curie and her husband declined to go to Stockholm to receive the prize in person; they were too busy with their work, and Pierre Curie, who disliked public ceremonies, was feeling increasingly ill. As Nobel laureates were required to deliver a lecture, the Curies finally undertook the trip in 1905. The award money allowed the Curies to hire their first laboratory assistant. Following the award of the Nobel Prize, and galvanised by an offer from the University of Geneva, which offered Pierre Curie a position, the University of Paris gave him a professorship and the chair of physics, although the Curies still did not have a proper laboratory. Upon Pierre Curie's complaint, the University of Paris relented and agreed to furnish a new laboratory, but it would not be ready until 1906.

In December 1904, Curie gave birth to their second daughter, Ève. She hired Polish governesses to teach her daughters her native language, and sent or took them on visits to Poland.

On 19 April 1906, Pierre Curie died in a road accident. Walking across the Rue Dauphine in heavy rain, he was struck by a horse-drawn vehicle and fell under its wheels, which fractured his skull and killed him instantly. Curie was devastated by her husband's death. On 13 May 1906 the physics department of the University of Paris decided to retain the chair that had been created for her late husband and offer it to Marie. She accepted it, hoping to create a world-class laboratory as a tribute to her husband Pierre. She was the first woman to become a professor at the University of Paris.

Curie's quest to create a new laboratory did not end with the University of Paris, however. In her later years, she headed the Radium Institute (Institut du radium, now Curie Institute, Institut Curie), a radioactivity laboratory created for her by the Pasteur Institute and the University of Paris. The initiative for creating the Radium Institute had come in 1909 from Pierre Paul Émile Roux, director of the Pasteur Institute, who had been disappointed that the University of Paris was not giving Curie a proper laboratory and had suggested that she move to the Pasteur Institute. Only then, with the threat of Curie leaving, did the University of Paris relent, and eventually the Curie Pavilion became a joint initiative of the University of Paris and the Pasteur Institute.

In 1910 Curie succeeded in isolating radium; she also defined an international standard for radioactive emissions that was eventually named for her and Pierre: the curie. Nevertheless, in 1911 the French Academy of Sciences failed, by one or two votes, to elect her to membership in the academy. Elected instead was Édouard Branly, an inventor who had helped Guglielmo Marconi develop the wireless telegraph. It was only over half a century later, in 1962, that a doctoral student of Curie's, Marguerite Perey, became the first woman elected to membership in the academy.

Despite Curie's fame as a scientist working for France, the public's attitude tended toward xenophobia—the same that had led to the Dreyfus affair—which also fuelled false speculation that Curie was Jewish. During the French Academy of Sciences elections, she was vilified by the right-wing press as a foreigner and atheist. Her daughter later remarked on the French press's hypocrisy in portraying Curie as an unworthy foreigner when she was nominated for a French honour, but portraying her as a French heroine when she received foreign honours such as her Nobel Prizes.

In 1911, it was revealed that Curie was involved in a year-long affair with physicist Paul Langevin, a former student of Pierre Curie's, a married man who was estranged from his wife. This resulted in a press scandal that was exploited by her academic opponents. Curie (then in her mid-40s) was five years older than Langevin and was misrepresented in the tabloids as a foreign Jewish home-wrecker. When the scandal broke, she was away at a conference in Belgium; on her return, she found an angry mob in front of her house and had to seek refuge, with her daughters, in the home of her friend Camille Marbo.

International recognition for her work had been growing to new heights, and the Royal Swedish Academy of Sciences, overcoming opposition prompted by the Langevin scandal, honoured her a second time, with the 1911 Nobel Prize in Chemistry. This award was "in recognition of her services to the advancement of chemistry by the discovery of the elements radium and polonium, by the isolation of radium and the study of the nature and compounds of this remarkable element". Because of the negative publicity due to her affair with Langevin, the chair of the Nobel committee, Svante Arrhenius, attempted to prevent her attendance at the official ceremony for her Nobel Prize in Chemistry, citing her questionable moral standing. Curie replied that she would be present at the ceremony, because "the prize has been given to her for her discovery of polonium and radium" and that "there is no relation between her scientific work and the facts of her private life".

She was the first person to win or share two Nobel Prizes, and remains alone with Linus Pauling as Nobel laureates in two fields each. A delegation of celebrated Polish men of learning, headed by novelist Henryk Sienkiewicz, encouraged her to return to Poland and continue her research in her native country. Curie's second Nobel Prize enabled her to persuade the French government to support the Radium Institute, built in 1914, where research was conducted in chemistry, physics, and medicine. A month after accepting her 1911 Nobel Prize, she was hospitalised with depression and a kidney ailment. For most of 1912, she avoided public life but did spend time in England with her friend and fellow physicist Hertha Ayrton. She returned to her laboratory only in December, after a break of about 14 months.

In 1912 the Warsaw Scientific Society offered her the directorship of a new laboratory in Warsaw but she declined, focusing on the developing Radium Institute to be completed in August 1914, and on a new street named Rue Pierre-Curie (today rue Pierre-et-Marie-Curie). She was appointed director of the Curie Laboratory in the Radium Institute of the University of Paris, founded in 1914. She visited Poland in 1913 and was welcomed in Warsaw but the visit was mostly ignored by the Russian authorities. The institute's development was interrupted by the First World War, as most researchers were drafted into the French Army; it fully resumed its activities after the war, in 1919.

World War I

During World War I, Curie recognised that wounded soldiers were best served if operated upon as soon as possible. She saw a need for field radiological centres near the front lines to assist battlefield surgeons, including to obviate amputations when in fact limbs could be saved. After a quick study of radiology, anatomy, and automotive mechanics, she procured X-ray equipment, vehicles, and auxiliary generators, and she developed mobile radiography units, which came to be popularly known as petites Curies ("Little Curies"). She became the director of the Red Cross Radiology Service and set up France's first military radiology centre, operational by late 1914. Assisted at first by a military doctor and her 17-year-old daughter Irène, Curie directed the installation of 20 mobile radiological vehicles and another 200 radiological units at field hospitals in the first year of the war. Later, she began training other women as aides.

In 1915, Curie produced hollow needles containing "radium emanation", a colourless, radioactive gas given off by radium, later identified as radon, to be used for sterilising infected tissue. She provided the radium from her own one-gram supply. It is estimated that over a million wounded soldiers were treated with her X-ray units. Busy with this work, she carried out very little scientific research during that period. In spite of all her humanitarian contributions to the French war effort, Curie never received any formal recognition of it from the French government.

Also, promptly after the war started, she attempted to donate her gold Nobel Prize medals to the war effort but the French National Bank refused to accept them. She did buy war bonds, using her Nobel Prize money. She said:

I am going to give up the little gold I possess. I shall add to this the scientific medals, which are quite useless to me. There is something else: by sheer laziness I had allowed the money for my second Nobel Prize to remain in Stockholm in Swedish crowns. This is the chief part of what we possess. I should like to bring it back here and invest it in war loans. The state needs it. Only, I have no illusions: this money will probably be lost.